Mate, the 2-4am window is basically the paranormal rush hour - whatever's on the other side clearly hasn't discovered flexi-time yet. 🕒
Had something similar in an old Victorian terrace I was renting in Nantwich about three years back. Three sharp knocks, pause, two knocks - same pattern every single night like clockwork. Started logging it properly with a Zoom H5 recorder I'd borrowed, and the audio picked up sub-frequencies that weren't audible to the naked ear. Genuinely sent a shiver down my spine when I reviewed the files.
Few things worth ruling out first though, because I've seen this community go full poltergeist on what turned out to be expanding pipes:
Thermal expansion in older plumbing (especially Victorian properties), Mice or squirrels in cavity walls - the little horrors are surprisingly rhythmic, Infrasound from nearby roads causing resonance in hollow walls
That said, if it's genuinely patterned and consistent, that's where it gets interesting. Random noise doesn't repeat in sequences. Something creating a deliberate 3-2 knock pattern night after night is either intelligent or the world's most haunted boiler.
What type of property are you in, and have you tried knocking back? The responses I documented after reciprocating were what really made my hair stand up.
Get yourself a decent audio recorder running overnight - even a Roland R-07 would do the job. Document everything with timestamps.
What's the exact pattern you're hearing?